Torsional Springs Free Position and Pre-Load:
Your torsional spring’s free position is the angle its legs make when no force is applied to it. When installing your torsional spring into your mechanism, though, your spring must be pre-loaded so that it stays in place and is not unstable. For this reason, you want to make sure that your spring’s free position is a few degrees greater so that its legs are more open. Therefore not only giving you the angle you need but it’ll give your torsional spring the stability it needs to function.